This is completely misguided for two reasons.

1) you're talking about ADHD which is a disability. It's like asking someone with no legs if they could sprout legs if the reason was compelling enough. The answer is still no.

2) If you were to counter the above by saying that, if you were compelled enough you might devote a small fortune and a few years training yourself and researching how to develop and use bionic legs, we then run into problem no 2: exceptional incentives / circumstances are not scalable, and the logic cannot be applied to problems of daily routine.

Back when I was a med student, I was expected to attend a clinic which started at 9. Unfortunately the local bus always arrived at that stop at 9:05, and the line was known for its flakiness. The route was 1h and 5min long, and I was about an hour's walk away from the stop myself. So in order to be at the hospital at 8:05 instead of 9:05, I aimed for the 7am bus, meaning I woke up at 5:30 to get to it. Except the 7am bus never showed up. So I waited another hour and got the 8am one, which inevitably arrived at 9:05.

When I got to the clinic 5 minutes late and got told off, I explained what happened, and the consultant said exactly the same thing you said: if there was a pot of money waiting you'd have been on time.

Yes except there wasn't, and I have to be at clinic every day, there was no way of knowing the first bus would not show up, and I can't afford to wake up at 4:30 everyday to get two buses ahead of the 8am one, just because some idiot thinks an imaginary pot of guilt-trip money would have instantly solved the problem.

I have a similar issue, I can find motivation to start something but then it spirals into other things.

For $100 million I would probably just learn to put on the scuba gear but for instance my mind would go to "I should make my own scuba gear". So for a personal project I start on something and decide I need something else, so then I want to make a tool to help me make that thing and so on. I think it's probably related to a shorter attention span so I'm working on that.

Learn how? Almost definitely.

Actually do it? That's a lot less certain than you would expect.

I would probably start. Since this hypothetical is a pretty simple one-off, I might even manage to generate enough executive functioning to follow through.

What I can tell you for certain is that I am still very excited to work on a custom keyboard project that I started 4 years ago. I have all the parts and equipment readily available at home, and plenty of free time. I have not worked on it at all over the past 4 years.

I do need a compelling reason to do something. I can't figure out how all these people get through what they do without wanting to jump out their office windows, to be honest.

Is it fun/interesting? Can I make it fun/interesting? Does it make me or save me money so I can do something fun/interesting?

If the answer is no to all of these questions, I'm going to have a bad time. Unfortunately, I'm that simple. I've gotten better at number two over the years, though.

Scuba diving sounds fun. I'd probably do it for less.